Uroporphyrinogen I

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Uroporphyrinogen I
Uroporphyrinogen I.svg
Preferred IUPAC name
3,3′,3′′,3′′′-[14,33,53,73-Tetrakis(2-hydroxy-2-oxoethyl)-11H,31H,51H,71H-1,3,5,7(2,5)-tetrapyrrolacyclooctaphane-13,34,54,74-tetrayl]tetrapropanoic acid
3D model (JSmol)
  • InChI=1S/C40H44N4O16/c45-33(46)5-1-17-21(9-37(53)54)29-14-26-19(3-7-35(49)50)23(11-39(57)58)31(43-26)16-28-20(4-8-36(51)52)24(12-40(59)60)32(44-28)15-27-18(2-6-34(47)48)22(10-38(55)56)30(42-27)13-25(17)41-29/h41-44H,1-16H2,(H,45,46)(H,47,48)(H,49,50)(H,51,52)(H,53,54)(H,55,56)(H,57,58)(H,59,60) ☒N
  • InChI=1/C40H44N4O16/c45-33(46)5-1-17-21(9-37(53)54)29-14-26-19(3-7-35(49)50)23(11-39(57)58)31(43-26)16-28-20(4-8-36(51)52)24(12-40(59)60)32(44-28)15-27-18(2-6-34(47)48)22(10-38(55)56)30(42-27)13-25(17)41-29/h41-44H,1-16H2,(H,45,46)(H,47,48)(H,49,50)(H,51,52)(H,53,54)(H,55,56)(H,57,58)(H,59,60)
  • O=C(O)CCc1c(c5[nH]c1Cc2[nH]c(c(c2CC(=O)O)CCC(=O)O)Cc3c(c(c([nH]3)Cc4c(c(c([nH]4)C5)CCC(=O)O)CC(=O)O)CCC(=O)O)CC(=O)O)CC(=O)O
Molar mass 836.804 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Uroporphyrinogen I is an isomer of uroporphyrinogen III, a metabolic intermediate in the biosynthesis of heme. A type of porphyria is caused by production of uroporphyrinogen I instead of III.

Biosynthesis and metabolism[edit]

In living organisms, uroporphyrinogen I occurs as a side branch of the main porphyrin synthesis pathway. In the normal pathway, the linear tetrapyrrole precursor preuroporphyrinogen (a substituted hydroxymethylbilane) is converted by the enzyme uroporphyrinogen-III cosynthase into the cyclic uroporphyrinogen III; which is then converted to coproporphyrinogen III on the way to porphyrins like heme. Uroporphyrinogen I is instead produced spontaneously from preuroporphyrinogen when the enzyme is not present.[1][2]

Uroporphyrinogen I synthesis from preuroporphyrinogen

The difference between the I and III forms is the arrangement of the four carboxyethyl groups (propionic acid, "P") and the four carboxymethyl groups (acetic acid, "A"). The non-enzymatic conversion to uroporphyrinogen I results in the sequence AP-AP-AP-AP, whereas the enzymatic conversion into uroporphyrinogen III leads to reversal of one AP-group and hence an AP-AP-AP-PA arrangement.

If synthesized, uroporphyrinogen I is then converted into coproporphyrinogen I by the same enzyme (uroporphyrinogen decarboxylase) that acts on the III form; but that product, which is cytotoxic, then accumulates causing the pathology congenital erythropoietic porphyria.[2]


  1. ^ Paul R. Ortiz de Montellano (2008). "Hemes in Biology". Wiley Encyclopedia of Chemical Biology. John Wiley & Sons. doi:10.1002/9780470048672.wecb221. ISBN 978-0470048672.
  2. ^ a b Sassa, S.; Kappas, A. (2000). "Molecular aspects of the inherited porphyrias". Journal of Internal Medicine. 247 (2): 169–178. doi:10.1046/j.1365-2796.2000.00618.x. PMID 10692079. S2CID 36820694.